Transmissions of commercial vehicles in particular often have auxiliary power take-offs by way of which additional aggregates of the commercial vehicle concerned can be connected to an auxiliary output of the transmission concerned and thereby be operated. For the operation of such additional aggregates a corresponding drive torque is picked up from the auxiliary power take-off concerned. To be able to couple and decouple the auxiliary power take-off according to need, a shifting element is usually associated with the auxiliary power take-off, such shifting elements being in most cases in the form of interlocking shifting elements such as claw clutches.
Besides fixed auxiliary power take-offs by means of which a particular additional aggregate can only be operated when the vehicle is at rest, the vehicle transmissions in commercial vehicles are often equipped with mobile auxiliary power take-offs by way of which a corresponding additional aggregate can be operated even while the motor vehicle is in motion. However, since additional aggregates usually only have a limited permissible operating range, a mobile auxiliary power take-off can only be activated in certain gears of the transmission.
DE 10 2008 040 757 A1 describes a method for coupling an auxiliary power take-off of a transmission, wherein during the course of the coupling, an interlocking shifting element of the auxiliary power take-off is actuated so as to close when all the conditions required for the coupling of the auxiliary power take-off are fulfilled. If the conditions are not fulfilled, the process starts afresh or reverts to one of the previous process steps. The driver of the vehicle must then himself establish the conditions required for the auxiliary power take-off to be coupled, but on the one hand this can be perceived as complicated and on the other hand as annoying if the vehicle driver has to repeat individual steps in the event that at the time when the coupling of the auxiliary power take-off is commanded, the necessary conditions are not fulfilled.